PR modula2/109586 cc1gm2 ICE when compiling large source files.

PR modula2/109586 cc1gm2 ICE when compiling large source files.

The function m2block_RememberConstant calls m2tree_IsAConstant.
However IsAConstant does not recognise TREE_CODE(t) ==
CONSTRUCTOR as a constant.  Without this patch CONSTRUCTOR
contants are garbage collected (and not preserved) resulting in
a corrupt tree and crash.

gcc/m2/ChangeLog:

	PR modula2/109586
	* gm2-gcc/m2tree.cc (m2tree_IsAConstant): Add (TREE_CODE
	(t) == CONSTRUCTOR) to expression.

Signed-off-by: Gaius Mulley <gaiusmod2@gmail.com>